/**
 * Copyright (c) 2006-2021 LOVE Development Team
 *
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
 *    appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 **/

#ifndef LOVE_REFERENCE_H
#define LOVE_REFERENCE_H

struct lua_State;

namespace love
{

/**
 * This class wraps the reference functionality built into
 * Lua, which allows C++ code to refer to Lua variables.
 **/
class Reference
{
public:

	/**
	 * Creates the reference object, but does not create
	 * the actual reference.
	 **/
	Reference();

	/**
	 * Creates the object and a reference to the value
	 * on the top of the stack.
	 **/
	Reference(lua_State *L);

	/**
	 * Deletes the reference, if any.
	 **/
	virtual ~Reference();

	/**
	 * Creates a reference to the value on the
	 * top of the stack.
	 **/
	void ref(lua_State *L);

	/**
	 * Unrefs the reference, if any.
	 **/
	void unref();

	/**
	 * Pushes the referred value onto the stack of the specified Lua coroutine.
	 * NOTE: The coroutine *must* belong to the same Lua state that was used for
	 * Reference::ref.
	 **/
	void push(lua_State *L);

private:

	// A pinned coroutine (probably the main thread) belonging to the Lua state
	// in which the reference resides.
	lua_State *pinnedL;

	// Index to the Lua reference.
	int idx;
};

} // love

#endif // LOVE_REFERENCE_H
